1. Field of the Invention
The present invention relates to exposure member drive control devices for controlling the variation of a diaphragm or shutter, and, more particularly, to a diaphragm drive control device for setting the diaphragm to a particular aperture value, and a rotary shutter drive control device for controlling the angle of opening of a rotary shutter.
2. Description of the Prior Art
When the variation of the size of aperture opening of the diaphragm is electrically controlled, the diaphragm must be initially set to a particular aperture value. For the initial setting purpose, the diaphragm is usually provided with a switch for detecting when its aperture size takes the particular value. If there is no detection output in the initial state, the diaphragm is driven to move toward either a maximum or a minimum value, and then stopped from further movement when the detection switch detects the particular aperture value. Thus, the diaphragm is set in an initial position.
Also, if there is a detection output in the initial state, the diaphragm is assumed to have the particular aperture value, permitting the subsequent operations to go on.
However, if the detection switch malfunctions, the initial presence of the detection output does not insure that the diaphragm is already set in the initial position of the particular aperture value, and the occurrence of the malfunction of the detection switch cannot be checked. Such problems have arisen even when the rotary shutter is set to the initial position.